Plasma processing apparatus

ABSTRACT

A plasma processing apparatus includes: a processing container; a processing gas supply unit; a mounting table configured to mount a to-be-processed substrate thereon; an upper electrode provided above the mounting table; a plasma generation unit configured to supply a high frequency power to generate plasma of the processing gas; an exhaust flow path formed by a side wall of the processing container and a side surface of the mounting table; a conductive rectification plate configured to adjust a flow of the processing gas discharged to outside of the processing container; a conductor arranged in the exhaust flow path at a position higher than the rectification plate and lower than the to-be-processed substrate to face at least a part of the upper electrode. A distance of the conductor in the height direction in relation to the to-be-processed surface of the substrate is set to be within a predetermined range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2014-254376, filed on Dec. 16, 2014, with the JapanPatent Office, the disclosure of which are incorporated herein in itsentirety by reference.

TECHNICAL FIELD

Various aspects and exemplary embodiments disclosed herein relate to aplasma processing apparatus.

BACKGROUND

In a semiconductor manufacturing process, a plasma processing apparatusthat executes a plasma processing for the purpose of, for example,deposition of a thin film or etching has been widely used. As the plasmaprocessing apparatus, a plasma chemical vapor deposition (CVD) apparatusthat performs a deposition processing of a thin film or a plasma etchingapparatus that performs an etching processing may be exemplified.

The plasma processing apparatus includes a processing containerconfigured to define a plasma processing space, a mounting tableconfigured to mount a to-be-processed substrate thereon within theprocessing container, an upper electrode provided above the mountingtable, and a gas supply system configured to introduce a processing gasrequired for a plasma reaction into the processing container. Inaddition, in order to turn the processing gas within the processingchamber into plasma, the plasma processing apparatus includes, forexample, a plasma generation mechanism configured to supply electronicenergy such as for example, microwaves or RF waves. In addition, in theplasma processing apparatus, an exhaust flow path for exhausting theprocessing gas to the outside of the processing container is formed bythe side wall of the processing container and the side surface of themounting table. In the exhaust flow path, a baffle plate is provided toadjust the flow of the processing gas. The baffle plate functions torectify the gas within the processing container so as to cause the gasto be uniformly exhausted. In addition, the baffle plate usually hasconductivity.

However, in the plasma processing apparatus, it has been known thatelectrons in the generated plasma are drawn to the conductive baffleplate and produce a reaction product on the surface of the baffle plate.Thus, a conductor is provided in the exhaust flow path in order to blockthe electrons. For example, there is a prior art in which a groundelectrode made of a conductor is arranged in the exhaust flow path at aposition that is higher than the baffle plate and lower than ato-be-processed substrate mounted on the mounting table so as to causethe electrons in the plasma to escape to the ground electrode. See, forexample, Japanese Patent Laid-Open No. 2007-258471.

SUMMARY

A plasma processing apparatus according to the present disclosureincludes: a processing container; a gas supply unit configured to supplya processing gas into the processing container; a mounting tableprovided within the processing container, and configured to mount ato-be-processed substrate thereon; an upper electrode provided at anupper side of the mounting table; a plasma generation unit configured tosupply a high frequency power to at least one of the upper electrode andthe mounting table to generate plasma of the processing gas within theprocessing container; an exhaust flow path formed by a side wall of theprocessing container and a side surface of the mounting table; aconductive rectification plate provided in the exhaust flow path, andconfigured to adjust a flow of the processing gas that is discharged tooutside of the processing container by the exhaust flow path; aconductor arranged in the exhaust flow path at a position higher thanthe rectification plate and lower than the to-be-processed substratemounted on the mounting table to face at least a part of the upperelectrode. A distance of the conductor in a height direction in relationto a to-be-processed surface of the to-be-processed substrate is set tobe within a predetermined range.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view illustrating a plasmaprocessing apparatus according to an exemplary embodiment.

FIG. 2A is a view illustrating an exemplary installation aspect ofconductors.

FIG. 2B is a view illustrating a state in which a conductor is onlyprovided on a side surface of a mounting table.

FIG. 3 is a view illustrating a state in which plasma is generated in aplasma processing apparatus of a comparative example.

FIG. 4 is a view illustrating a state in which plasma is generated inthe plasma processing apparatus of the present exemplary embodiment.

FIG. 5 is a view illustrating etching rates in a case where organicfilms of wafers were etched by a predetermined processing gas.

FIG. 6 is a view illustrating an etching rate in a case where oxidefilms of wafers were etched by a predetermined processing gas.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

In the prior art described above, an electrode facing the upperelectrode does not exist in the exhaust flow path. Therefore, thegenerated plasma is concentrated to the central portion of theto-be-processed substrate mounted on the mounting table so that theetching rate in the central portion of the substrate is high and theetching rate in the peripheral portion is lowered. As a result, there isa problem in that the uniformity of the etching rate of theto-be-processed substrate is deteriorated.

In one exemplary embodiment, a plasma processing apparatus disclosedherein includes: a processing container; a gas supply unit configured tosupply a processing gas into the processing container; a mounting tableprovided within the processing container, and configured to mount ato-be-processed substrate thereon; an upper electrode provided at anupper side of the mounting table; a plasma generation unit configured tosupply a high frequency power to at least one of the upper electrode andthe mounting table to generate plasma of the processing gas within theprocessing container; an exhaust flow path formed by a side wall of theprocessing container and a side surface of the mounting table; aconductive rectification plate provided in the exhaust flow path, andconfigured to adjust a flow of the processing gas that is discharged tooutside of the processing container by the exhaust flow path; aconductor arranged in the exhaust flow path at a position higher thanthe rectification plate and lower than the to-be-processed substratemounted on the mounting table to face at least a part of the upperelectrode. A distance of the conductor in a height direction in relationto a to-be-processed surface of the to-be-processed substrate is set tobe within a predetermined range.

In addition, in one exemplary embodiment of the plasma processingapparatus disclosed herein, the conductor is provided in the exhaustflow path on at least one of the side wall side of the processingcontainer and the side surface side of the mounting table.

According to various aspects and exemplary embodiments of the presentdisclosure, a plasma processing apparatus is realized which is capableof improving in-plane uniformity of etching of a to-be-processedsubstrate.

Hereinafter, various exemplary embodiments will be described in detailwith reference to the accompanying drawings. The same or correspondingparts in each of the drawings will be denoted by the same referencenumerals.

Overall Configuration of Plasma Processing Apparatus

First, an overall configuration of a plasma processing apparatus 1according to an exemplary embodiment will be described with reference toFIG. 1. FIG. 1 is a vertical cross-sectional view illustrating a plasmaprocessing apparatus according to an exemplary embodiment. In thepresent exemplary embodiment, by way of an example, a parallel flatplate type plasma processing apparatus 1 will be described in which alower electrode (mounting table 20) and an upper electrode 25 (showerhead) are arranged to face each other within the processing container10, and a gas is supplied to the inside of the processing container 10from the upper electrode 25.

As illustrated in FIG. 1, the plasma processing apparatus 1 includes,for example, a processing container 10 that is formed of a conductivematerial such as, for example, aluminum having a surface subjected to analumite treatment (anodizing treatment), and a gas supply source 15configured to supply a gas into the processing container 10. Theprocessing container 10 is grounded. The processing container 10 definesa plasma processing space A therein. In the inner wall of the processingcontainer 10, a portion facing the plasma processing space A is coveredwith a volatile material 109 such as, for example, silicon or quartz.The processing container 10 is an example of the processing container.The gas supply source 15 supplies a specific gas in each plasmaprocessing step such as, for example, etching or cleaning. The gassupply source 15 is an example of the gas supply unit.

The processing container 10 is electrically grounded, and includes amounting table 20 therein so as to mount a wafer W thereon. The wafer Wis an example of the to-be-processed substrate, and is applicable to,for example, a flat panel substrate. The mounting table 20 functions asa lower electrode. In the ceiling portion, an upper electrode 25 isprovided to face the mounting table 20.

On the top surface of the mounting table 20, an electrostatic chuck 106is provided to electrostatically attract the wafer W. The electrostaticchuck 106 is formed in a structure in which a chuck electrode 106 a issandwiched between insulation members 106 b. A direct current (DC)voltage source 112 is connected to the chuck electrode 106 a, and when aDC voltage is applied to the chuck electrode 106 a from the DC voltagesource 112, the wafer W is attracted to the electrostatic chuck 106 by aCoulomb force. On the peripheral edge of the electrostatic chuck 106, afocus ring 101 formed of, for example, silicon, is disposed in order toenhance the in-plane uniformity of etching.

The mounting table 20 is supported by an electrode (lower electrode) 104of a conductor such as, for example, aluminum. Within the lowerelectrode 104, a coolant flow path 104 a is formed. In the coolant flowpath 104 a, for example, cooling water is circulated as a proper coolantso as to cool the wafer W.

A heat transfer gas supply source 85 causes a heat transfer gas such as,for example, helium gas (He) or argon gas (Ar), to pass through a gassupply line 130 so as to supply the heat transfer gas to the spacebetween the electrostatic chuck 106 and the wafer W. With thisconfiguration, the electrostatic chuck 106 is subjected to a temperaturecontrol by the cooling water circulated in the coolant flow path 104 a,and the heat transfer gas supplied to the rear surface of the wafer W.

The mounting table 20 is supported on the support member 105 via aholding member 103. The support member 105 is formed of an insulatingmaterial, and places the lower electrode 104 in a floating state byinsulating it from the processing container 10.

A first high frequency power supply 32 is electrically connected to theupper electrode 25 via a first matcher 33. A second high frequency powersupply 35 is electrically connected to the lower electrode 104 via asecond matcher 34. The first high frequency power supply 32 supplies afirst high frequency power of for example, 60 MHz to the upper electrode25. The second high frequency power supply 35 supplies a second highfrequency power of, for example, 13.56 MHz to the lower electrode 104.The high frequency power connection type may a lower two-frequency typeor any other type, besides the upper and lower two-frequency type.

The first and second matchers 33, 34 are intended to match a loadimpedance to internal (or output) impedances of the first and secondhigh frequency power supplies 32, 35, respectively, and function to makethe internal impedances of the first and second high frequency powersupplies 32, 35 apparently coincide with the load impedance when plasmais generated within the processing container 10.

The first and second high frequency power supplies 32, 35 are examplesof the power supplies that apply the energy of electromagnetic waves tothe processing container 10. As another example of the power supply thatapplies the energy of electromagnetic waves to the processing container10, microwave plasma and inductively coupled plasma (ICP) may beexemplified.

The upper electrode 25 is attached to the ceiling portion of theprocessing container 10 via a shield ring 40 that covers the peripheryof the upper electrode 25. The upper electrode 25 is electricallygrounded. A portion of the upper electrode 25 that faces the plasmaprocessing space A is covered with a volatile material 100 such as, forexample, silicon or quartz.

The upper electrode 25 includes a gas inlet 45 formed therein so as tointroduce the gas from the gas supply source 15. In addition, the upperelectrode 25 is provided with a center side diffusion chamber 50 a andan edge side diffusion chamber 50 b therein. The center side diffusionchamber 50 a and the edge side diffusion chamber 50 b are branched fromthe gas inlet 45 and diffuse the gas.

A plurality of gas supply holes 55 are formed in the upper electrode 25to supply the gas from the diffusion chambers 50 a, 50 b to the insideof the processing container 10. Each gas supply hole 55 is arranged tosupply the gas to the space between the wafer W mounted on the lowerelectrode and the upper electrode 25.

The gas from the gas supply source 15 is supplied to the diffusionchambers 50 a, 50 b through the gas inlet 45, diffused in the diffusionchambers 50 a, 50 b to be distributed to respective gas supply holes 55,and then introduced into the processing container 10 toward the lowerelectrode from the gas supply holes 55. With this configuration, theupper electrode 25 also functions as a gas shower head that supplies agas.

An annular exhaust flow path 62 is formed between the side wall 102 ofthe processing container 10 and the side surface of the mounting table20. The inner peripheral surface of the exhaust flow path 62 is coveredwith a sprayed coating 107 that contains yttrium oxide. The exhaust flowpath 62 is provided with a rectification plate (baffle plate) 108. Therectification plate (baffle plate) 108 adjusts the flow of theprocessing gas discharged to the outside of the processing container 10by the exhaust flow path 62. The rectification plate (baffle plate) 108is formed of a conductive material such as, for example, a metal. Anexhaust pipe 60 that forms an exhaust port 61 is provided in the bottomportion of the exhaust flow path 62. An exhaust apparatus 65 isconnected to the exhaust pipe 60. The exhaust apparatus 65 decompressesthe processing space within the processing container 10 to apredetermined vacuum degree with a vacuum pump (not illustrated).

In the exhaust flow path 62, a conductor 201 and a conductor 202 areprovided on the side wall 102 of the processing container 10 and theside surface of the mounting table 20, respectively. The conductor 201and the conductor 202 are arranged annularly to be orthogonal to theexhaust flow path 62. The conductor 201 and the conductor 202 are formedof a conductor such as, for example, silicon. In addition, theconductors 201 and 202 may be formed of, for example, polysilicon, SiC,or glassy carbon. The installation aspect of the conductor 201 and theconductor 202 will be described below.

On the side wall of the processing container 10, a gate valve G isprovided. The gate valve G opens/closes a carry-in/out port when a waferW is carried into or carried out from the processing container 10.

A plasma processing is performed on a wafer W by the plasma processingapparatus 1 configured as described above. For example, in the casewhere an etching processing is performed, the opening/closing of thegate valve G is controlled first, and the wafer W is carried into theprocessing container 10 and mounted on the mounting table 20 byelectrostatic attraction. Subsequently, an etching gas is introduced,and the first high frequency power and the second high frequency powerare supplied to the upper electrode 25 and the lower electrode 104,respectively, so that plasma is generated. A desired processing such as,for example, the plasma etching, is performed on the wafer W by thegenerated plasma. After the processing, the opening/closing of the gatevalve G is controlled, and the wafer W is carried out from theprocessing container 10.

Next, descriptions will be made on the installation aspect of theconductor 201 and the conductor 202 illustrated in FIG. 1. FIG. 2A is aview illustrating an exemplary installation aspect of the conductors. Asillustrated in FIG. 2A, the conductor 201 and the conductor 202 arearranged in the exhaust flow path 62 at a position that is higher thanthe baffle plate 108 and lower than the wafer W mounted on the mountingtable 20 to face at least a part of the upper electrode 25. In addition,the conductor 201 and the conductor 202 may be arranged to overlap witheach other in the central area of the exhaust flow path 62. Morespecifically, the conductor 201 is provided on the side wall 102 of theprocessing container 10, and arranged at a position that is higher thanthe baffle plate 108 and lower than the wafer W mounted on the mountingtable 20 to face at least a part of the upper electrode 25. The distanceL1 between the conductor 201 and the to-be-processed surface of thewafer W along the height direction in relation to the to-be-processedsurface of the wafer W may be, for example, 1 mm to 70 mm. The distanceL1 is set to be within a range where the conductor 201 is made tofunction as a ground electrode for the upper electrode 25. In addition,the conductor 202 is provided on the side surface of the mounting table20, and arranged at a position that is higher than the baffle plate 108and lower than the wafer W mounted on the mounting table 20 to face atleast a part of the upper electrode 25. The distance L2 between theconductor 202 and the to-be-processed surface of the wafer W along theheight direction in relation to the to-be-processed surface of the waferW may be 15 mm to 85 mm. The distance L2 is set to be within a rangewhere the conductor 202 is made to function as a ground electrode forthe upper electrode 25. In addition, the distance L3 between theconductor 201 and the conductor 202 along the height direction inrelation to the to-be-processed surface of the wafer W may be 20 mm to40 mm.

In addition, the conductor 201 and the conductor 202 may be arranged topartially overlap with each other when viewed in the height direction inrelation to the to-be-processed surface of the wafer W. By this, it ispossible to avoid the infiltration of the particles existing in theexhaust flow path 62 into the plasma processing space A of theprocessing container 10. In the case where the conductor 201 and theconductor 202 are arranged to partially overlap with each other, theratio of the width L4 of the overlapping portion between the conductor201 and the conductor 202 in relation to the conductor 201 or theconductor 202 may be set to 1.5% to 22.5%, preferably 1.5% to 15%. Whenthe conductor 201 and the conductor 202 are arranged in the exhaust flowpath 62 within the above-mentioned ranges, respectively, the exhaustwithin the processing container 10 can be uniformly and efficientlyperformed. In addition, because the plasma region generated within theprocessing container 10 is uniformly widened while increasing ananode/cathode (A/C) ratio, the processing on the wafer W can beuniformly performed.

In addition, while the foregoing description has illustrated an examplein which the conductor 201 and the conductor 202 are arranged topartially overlap with each other when viewed in the height direction inrelation to the to-be-processed surface of the wafer W, the conductor201 and the conductor 202 may be arranged not to partially overlap witheach other.

Here, the function of the conductor 201 and the conductor 202 as aground electrode will be described.

First, as a comparative example, descriptions will be made on a plasmaprocessing apparatus that does not include a conductor in the exhaustflow path 62. FIG. 3 is a view illustrating a state in which plasma isgenerated in the plasma processing apparatus of the comparative example.The plasma processing apparatus of the comparative example is differentfrom the plasma processing apparatus 1 of the present exemplaryembodiment in that it does not include a conductor in the exhaust flowpath 62, and the other features are the same as those of the plasmaprocessing apparatus 1 of the present exemplary embodiment. Thus, inFIG. 3 to be described below, the same components as those of thepresent exemplary embodiment will be denoted by the same referencenumerals.

The plasma processing apparatus of the comparative example does notinclude a conductor in the exhaust flow path 62. In other words, in theexhaust flow path 62, the upper electrode 25 and a counter electrode arepositioned far away from each other (while the baffle plate isapparently illustrated as a counter electrode, a function as the counterelectrode is not acting). For this reason, as illustrated in FIG. 3, inthe case where plasma P is generated within the processing container 10,the generated plasma P wraps around in the direction of the conductivebaffle plate 108 provided in the exhaust flow path 62, and isconcentrated to a position above the central portion of the wafer Wmounted on the mounting table 20. As a result, the difference betweenthe etching rate corresponding to the central portion of the wafer W andthe etching rate corresponding to the peripheral edge of the wafer W mayincrease, which may deteriorate the uniformity of the etching rate ofthe wafer W.

With respect to this, descriptions will be made on the plasma processingapparatus 1 of the present exemplary embodiment. FIG. 4 is a viewillustrating a state in which plasma is generated in the plasmaprocessing apparatus of the present exemplary embodiment. In the plasmaprocessing apparatus 1 of the present exemplary embodiment, theconductor 201 and the conductor 202 are arranged in the exhaust flowpath 62 at a position that is higher than the baffle plate 108 and lowerthan the wafer W mounted on the wafer W to face at least a part of theupper electrode 25. For example, etching was performed by setting thedistances L1, L2, L3, and L4 to 30 mm, 66 mm, 30.5 mm, and 6.5 mm,respectively, so that the conductor 201 and the conductor 202 were setwithin the range that allows the conductor 201 and the conductor 202 tofunction as a ground electrode for the upper electrode 25.

As illustrated in FIG. 4, in the case where plasma P′ is generatedwithin the processing container 10, the generated plasma P′ expands tothe upper side of the central portion of the wafer W and the upper sideof the conductor 201 and the conductor 202 without warping around in thedirection of the conductive baffle plate 108 provided in the exhaustflow path 62. As a result, the different between the etching ratecorresponding to the central portion of the wafer W and the etching ratefor the peripheral edge of the wafer W is suppressed so that thein-plane uniformity of the wafer W is improved.

In addition, while FIG. 2A illustrates an example in which the conductor201 is provided on the side wall 102 of the processing container 10, andthe conductor 202 is provided on the side surface of the mounting table20, the technique disclosed herein is not limited thereto. For example,only the conductor 201 may be provided on the side wall 102 of theprocessing container 10, or only the conductor 202 may be provided onthe side surface of the mounting table 20. For example, a conductor maybe provided in an annular shape in the exhaust flow path 62 on at leastone of the side wall 102 of the processing container 10 and the sidesurface of the mounting table 20 such that the conductor is orthogonalto the cross-section of the exhaust flow path 62. FIG. 2B illustrates,as an example, a state in which the conductor 201 is omitted and onlythe conductor 202 is provided on the side surface of the mounting table20.

In addition, in terms of increasing an anode/cathode (A/C) ratio, theconductors may be provided on both the side wall 102 of the processingcontainer 10 and the side surface of the mounting table 20 in theexhaust flow path 62, respectively. The A/C ratio increases as the areaof the anode side increases in relation to the area of the cathode side.When the conductors are provided on both the side wall 102 of theprocessing container 10 and the side surface of the mounting table 20,respectively, in the exhaust flow path 62, the apparent area of theanode side increases so that the A/C ratio increases. On the contrary, asputtering force to the side wall 102 of the processing container 10—theanode—decreases, and as a result, the consumption of a member issuppressed.

Next, descriptions will be made on an effect (etching rate) obtained bythe plasma processing apparatus of the present exemplary embodiment.FIG. 5 is a view representing etching rates when organic films of waferswere etched by using a predetermined processing gas.

In FIG. 5, the horizontal axis represents a diametric location [mm] on awafer W with reference to the position of the center of the wafer W, andthe vertical axis represents an etching rate [nm/min] in the case wherean organic film on the wafer

W was etched by a predetermined processing gas.

In addition, in FIG. 5, Graph 252 is a graph representing an etchingrate in the case where an organic film of a wafer W was etched by usinga plasma processing apparatus of the comparative example which did notinclude a conductor in the exhaust flow path 62. Graph 254 is a graphillustrating an etching rate in the case where an organic film of awafer W was etched by using the plasma processing apparatus 1 of thepresent exemplary embodiment in which the conductor 201 and theconductor 202 were provided on the side wall 102 of the processingcontainer 10 and the side surface of the mounting table 20 in theexhaust flow path 62, respectively. In addition, in Graph 254, theconductor 201 and the conductor 202 were arranged such that thedistances L1, L2, L3, and L4 were set to 30 mm, 66 mm, 30.5 mm, and 6.5mm, respectively. Graph 256 is a graph representing an etching rate inthe case where an organic of a wafer W was etched by using the plasmaprocessing apparatus 1 of the present exemplary embodiment in which theconductor 202 was provided on the side surface of the mounting table 20in the exhaust flow path 62 and a dielectric was provided on the sidewall 102 of the processing container 10 instead of the conductor 201. Inaddition, the dielectric provided instead of the conductor 201 is formedby a dielectric such as, for example, quartz. In addition, in Graph 256,the conductor 201 and the dielectric were arranged such that thedistances L1, L2, L3, and L4 were set to 30 mm, 66 mm, 30.5 mm, and 6.5mm, respectively.

As represented by Graph 252 in FIG. 5, in the plasma processingapparatus of the comparative example which did not include a conductorin the exhaust flow path 62, the average etching rate along thediametric direction of the wafer W was 25.9 mm/min, and the deviationfrom the mean etching rate was ±23.8%. Both the average etching rate andthe deviation did not satisfy a predetermined allowable specification.

Whereas, as represented by Graph 254 in FIG. 5, in the plasma processingapparatus 1 of the present exemplary embodiment in which the conductor201 and the conductor 202 were provided on the side wall 102 of theprocessing container 10 and the side surface of the mounting table 20 inthe exhaust flow path 62, respectively, the average etching rate alongthe diametric direction of the wafer W was 23.9 nm/min, and thedeviation from the average etching rate was ±17.9%. Both the averageetching rate and the deviation satisfied a predetermined allowablespecification. In addition, as represented by Graph 256 in FIG. 5, inthe plasma processing apparatus 1 of the present exemplary embodiment inwhich the conductor 202 was provided on the side surface of the mountingtable 20 in the exhaust flow path 62 and the dielectric plate wasprovided on the side wall 102 of the processing container 10 instead ofthe conductor 201, the average etching rate along the diametricdirection of the wafer W was 21.2 nm/min, and the deviation from theaverage etching rate was ±19.4%. Both the average etching rate and thedeviation satisfied a predetermined allowable specification. That is, inthe case where a conductor was provided on at least one of the side wall102 of the processing container 10 and the side surface of the mountingtable 20 in the exhaust flow path 62, the uniformity of the etching rateof the wafer W was improved as compared to the case where no conductorwas provided in the exhaust flow path 62. This is thought to have beenresulted from the fact that in the case where the conductor is providedon at least one of the side wall 102 of the processing container 10 andthe side surface of the mounting table 20 in the exhaust flow path 62,the plasma is spread to the upper side of the central portion of thewafer W and to the upper side of the conductor 201 and the conductor 202by the function of the conductor as a ground electrode.

FIG. 6 is a view illustrating an etching rate in a case where an oxidefilm of a wafer was etched by a predetermined processing gas. In FIG. 6,the horizontal axis represents a diametric position [mm] of a wafer Wwith reference to the central position thereof, and the vertical axisrepresents an etching rate [nm/min] in a case where an oxide film of awafer W was etched by a predetermined processing gas.

In addition, in FIG. 6, Graph 262 is a graph that represents an etchingrate in the case where an oxide film of a wafer W was etched by using aplasma processing apparatus of a comparative example in which noconductor was provided in the exhaust flow path 62. Graph 264 is a graphthat represents an etching rate in the case where an oxide film of awafer W was etched by using the plasma processing apparatus 1 of thepresent exemplary embodiment in which the conductor 201 and theconductor 202 were provided on the side wall 102 of the processingcontainer 10 and the side surface of the mounting table 20 in theexhaust flow path 62, respectively. In addition, in Graph 264, theconductor 201 and the conductors 202 were arranged such that thedistances L1, L2, L3, and L4 were set to 30 mm, 66 mm, 30.5 mm, and 6.5mm, respectively. Graph 266 is a graph that represents an etching ratein the case where an oxide film of a wafer W was etched by using aplasma processing apparatus 1 of the present exemplary embodiment inwhich the conductor 201 was provided on the side wall 102 of theprocessing container 10, and the dielectric was provided on the sidesurface of the mounting table 20, instead of the conductor 202. Inaddition, the dielectric that replaced the conductor 202 was formed of adielectric material such as, for example, quartz. In addition, in Graph266, the conductor 201 and the dielectric were arranged such that thedistances L1, L2, L3, and L4 were set to 30 mm, 66 mm, 30.5 mm, and 6.5mm, respectively. Graph 268 is a graph that represents an etching ratein the case where an oxide film of a wafer W was etched by using theplasma processing apparatus 1 of the present exemplary embodiment inwhich the conductor 202 was provided on the side surface of the mountingtable 20 in the exhaust flow path 62, and in addition, the dielectricwas provided on the side wall 102 of the processing container 10 insteadof the conductor 201. In addition, the dielectric that replaces theconductor 201 is formed of a dielectric material such as, for example,quartz. In addition, in Graph 268, the dielectric and the conductor 202were arranged such that the distances L1, L2, L3, and L4 were set to 30mm, 66 mm, 30.5 mm, and 6.5 mm, respectively.

As represented by Graph 262 of FIG. 6, in the plasma processingapparatus of a comparative example that did not include a conductor inthe exhaust flow path 62, the average etching rate along the diametricdirection of the wafer W was 66.1 mm/min, and the deviation from theaverage etching rate was ±10.9%. Both the average etching rate and thedeviation did not satisfy the predetermined allowable specifications.

On the contrary, as represented by Graph 264 in FIG. 6, in the plasmaprocessing apparatus 1 of the present exemplary embodiment in which theconductor 201 and the conductor 202 were provided on the side wall 102of the processing container 10 and the side surface of the mountingtable 20 in the exhaust flow path 62, respectively, the average etchingrate according to the diametric direction of the wafer W was 59.3nm/min, and the deviation from the average etching rate was ±4.4%. Boththe average etching rate and the deviation satisfied the predeterminedallowable specifications. In addition, as represented by Graph 266 inFIG. 6, in the plasma processing apparatus 1 of the present exemplaryembodiment in which the conductor 201 was provided on the side wall 102of the processing container 10, and a dielectric plate was provided onthe side surface of the mounting table 20 instead of the conductor 202,the average etching rate according to the diametric direction of thewafer W was 59.7 nm/min and the deviation from the average etching ratewas ±7.3%. Both the average etching rate and the deviation satisfied thepredetermined allowable specification. In addition, as represented byGraph 268 in FIG. 6, in the plasma processing apparatus 1 of the presentexemplary embodiment in which the conductor 202 was provided on the sidesurface of the mounting table 20 in the exhaust flow path 62 and thedielectric plate was provided on the side wall 102 of the processingcontainer 10, instead of the conductor 201, the average etching ratealong the diametric direction of the wafer W was 58.6 nm/min and thedeviation from the average etching rate was ±5.8%. Both the averageetching rate and the deviation satisfied the predetermined allowablespecifications. That is, in the case where a conductor was provided onat least one of the side wall 102 of the processing container 10 and theside surface of the mounting table 20 in the exhaust flow path 62, theuniformity of the etching rate of the wafer W was improved as comparedto a case in which no conductor is provided in the exhaust flow path 62.It is believed that this is resulted from the fact that in the casewhere the conductor is provided on at least one of the side wall 102 ofthe processing container 10 and the side surface of the mounting table20 in the exhaust flow path 62, plasma is spread to the upper side ofthe central portion of the wafer W and to the upper side of theconductor 201, 202 due to the function of the conductor as a groundelectrode.

As described above, in the plasma processing apparatus 1 of the presentexemplary embodiment, the conductor 201 and the conductor 202 werearranged in the exhaust flow path 62 to face at least a part of theupper electrode 25, and the distance of the conductors in the heightdirection in relation to the to-be-processed surface of the wafer W wasset to be within a predetermined range. By this, when plasma P′ isgenerated within the processing container 10, the generated plasma P′ isspread to the upper side of the central portion of the wafer W and tothe upper side of the conductor 201 and the conductor 202 withoutwarping around in the direction of the conductive baffle plate 108provided in the exhaust flow path 62. As a result, a difference betweenthe etching rate that corresponds to the central portion of the wafer Wand the etching rate that corresponds to the peripheral edge of thewafer W is suppressed such that the uniformity of the etching rate ofthe wafer W can be improved.

From the foregoing, it will be appreciated that various exemplaryembodiments of the present disclosure have been described herein forpurposes of illustration, and that various modifications may be madewithout departing from the scope and spirit of the present disclosure.Accordingly, the various exemplary embodiments disclosed herein are notintended to be limiting, with the true scope and spirit being indicatedby the following claims.

What is claimed is:
 1. A plasma processing apparatus comprising: aprocessing container; a gas supply unit configured to supply aprocessing gas into the processing container; a mounting table providedwithin the processing container, and configured to mount ato-be-processed substrate thereon; an upper electrode provided at anupper side of the mounting table; a plasma generation unit configured tosupply a high frequency power to at least one of the upper electrode andthe mounting table to generate plasma of the processing gas within theprocessing container; an exhaust flow path formed by a side wall of theprocessing container and a side surface of the mounting table; aconductive rectification plate provided in the exhaust flow path, andconfigured to adjust a flow of the processing gas that is discharged tooutside of the processing container by the exhaust flow path; and aconductor arranged in the exhaust flow path at a position higher thanthe rectification plate and lower than the to-be-processed substratemounted on the mounting table to face at least a part of the upperelectrode, a distance of the conductor in a height direction in relationto a to-be-processed surface of the to-be-processed substrate being setto be within a predetermined range.
 2. The plasma processing apparatusof claim 1, wherein the conductor is provided in the exhaust flow pathon at least one of the side wall side of the processing container andthe side surface side of the mounting table.